Services of providing information indicative of an environment on roads to vehicles or various types of information terminals have been developed progressively in recent years, and, as one example of such a system for monitoring the road environment, a road monitoring system described in Patent Document 1 is known.
The road monitoring system described in Patent Document 1 takes pictures of the driving environment on the road with a plurality of imaging cameras 30a to 30c set up at predetermined spacing on the side of the road, as shown in FIG. 28. The taken images are analyzed to determine an event happening on the road. If, for example, a plurality of fallen objects D is detected to be present 1 km ahead of a vehicle C through such a determination, this detection result is displayed on an information display panel 61. In this determination of events, an obstacle or a traffic congestion situation is detected through an analysis of the taken images.